Fire masks, Hampstead, London, 1941. One of Miller’s most famous war shots, this was part of a Vogue feature to show how British women were coping with the war. Photograph: The Lee Miller Archives

On 30 April 1945, Lee Miller and her colleague and sometime lover, David Scherman, arrived at Dachau. The only woman photographer at the camp, Miller documented what she found there quickly, but with great precision. On a railway line close by was a train full of thousands of corpses, which she now shot from a variety of angles, a shocked witness in almost every frame. Inside the camp, she and Scherman were mobbed by survivors. But still, she would not be distracted: captured Dachau guards, the women who’d worked in the camp brothel, a Viennese doctor and the Gypsy woman under her care – nothing and no one escaped her eye. By the time she and Scherman left for Munich that afternoon, they were, reports her biographer Carolyn Burke, “gulping for air and violence”. The word was that the city, the birthplace of the horror she had just witnessed, was about to fall. They wanted to help it on its way.

Like the women she photographed, Miller was plucky, determined and in possession of a robust sense of humour

What happened next is well known. The US 45th Division having already taken Munich, Miller and Scherman proceeded to the house at 16 Prinzregentenplatz where Hitler had lived since the late 1920s. Miller peered at the Führer’s mediocre art and inspected his china, and then the couple adjourned to his bathroom. Neither of them had bathed for weeks, and they now took turns in his tub, photographing each other as they did so. Scherman’s image of Miller, intimate and yet so uncomfortable, has since become famous, the Dachau mud she had trod into Hitler’s bathmat not only a symbol of the stain he had left on Europe, but of the indelible images that would all but destroy her sanity in the coming years.

The Imperial War Museum’s forthcoming exhibition of Miller’s war work will include this unnerving image. But it will also feature many other equally brilliant but less well known photographs, some of which have not been printed since they were first taken 70 years ago. “The project began several years ago,” says its curator, Hilary Roberts. “It came out of a conversation with Miller’s son, Antony Penrose. Our feeling was that people know relatively little of her war work, the majority of which was concerned with the experiences of women. The idea was to look at it, and along the way to ask the question: does gender make a difference?” Has she been able to draw any conclusions about this? “Gender doesn’t affect ability. But it can certainly affect access, and has a profound influence on subject.”

Homeless children, Budapest, 1946. Miller’s critical view of the part played by Germany’s allies in the war was always tempered by compassion. Photograph: Lee Miller Archives

Miller revealed to the world not only the worst horrors of the war, but the very best of herself

Miller’s experience of the war reflects those of many other women: it liberated her, allowing her to fulfil her true potential for the first time (until its outbreak, she had been working as a fashion and fine art photographer). Appointed Vogue’s official war photographer in London, she covered the blitz, the aftermath of D-day, the liberation of Paris, and the movement of refugees through Europe. But she would also suffer, once it was all over, from what would now be called post-traumatic stress disorder. “Miller had been raped as a child,” says Roberts. “This made her particularly vulnerable to trauma later in life, and she found it impossible to settle back into peacetime.” She began to drink heavily and, until her death in 1977, suffered long bouts of depression.

The exhibition will make sense of this decline; visitors will be able to hear a recording of Miller, briefly back home in America after the war, describing the camps at Buchenwald and Dachau, her voice full of sadness. But it will also reveal, in 150 images, the scope of her unique talent. Like the women she photographed during the blitz and afterwards, she was plucky, determined and in possession of a robust sense of humour. Her work mattered deeply, and in doing it so well, she revealed to the world not only the worst horrors of the war, but the very best of herself.

Lee Miller: A Woman’s War is at the Imperial War Museum, London, 15 Oct-24 April 2016. An accompanying book, Lee Miller: A Woman’s War by Hilary Roberts, featuring 156 illustrations, is published by Thames & Hudson, 5 Oct, £29.95 .